Problem: Simplify the following expression: $q = \dfrac{1}{10t} - \dfrac{3}{2t}$
Answer: In order to subtract expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $10t$ and $2t$ $\lcm(10t, 2t) = 10t$ $ q = \dfrac{1}{1} \cdot \dfrac{1}{10t} - \dfrac{5}{5} \cdot \dfrac{3}{2t} $ $q = \dfrac{1}{10t} - \dfrac{15}{10t}$ $q = \dfrac{1 -15}{10t}$ $q = \dfrac{-14}{10t}$ Simplify the expression by dividing the numerator and denominator by 2: $q = \dfrac{-7}{5t}$